Known working machines, such as telescopic handlers have a boom, or arm that is able to lift loads. The boom is raised and lowered relative to a chassis of the telescopic handler by a hydraulically actuated lift ram. By knowing various dimensions of the machine, including the angle of the arm relative to the chassis of the machine it is possible to monitor the change of hydraulic pressure in the lift ram to calculate an estimate of the weight of the load lifted. However, calculating the load from hydraulic pressure is not very accurate because of fluctuations in pressure under different conditions, for example, crowding/dumping of the load, changing the lift speed of the arm, changing the extension on the arm, changing the angle of the arm relative to the chassis.
In order to improve the accuracy of weighing the operation of the machine may be restricted. For example weighing may only take place under certain conditions. In one example weighing can only be done at a predefined arm angle. In another example, it is necessary to raise the arm at a predetermined speed as well as ensuring that the engine speed is kept at a predetermined rpm. Such prior art weighing systems limit the operation of the machine and therefore the machine takes longer to carry out specific tasks, for example loading grain or the like into a lorry. Furthermore, such prior art weighing systems require a high level of skill from the operator in order to achieve more accurate results.